Journal of Engineering and Technological Sciences
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Mechanical Behavior of Dam Foundation with Vertical Sand Drain, Case Study: Sombar Dam
Get PDFInstalling vertical sand drains is a traditional dam foundation consolidation solution that is economical and provides good drainage efficiency. Vertical sand drains can shorten the path of water flow inside the soil and speeds up soil consolidation. This study investigated the effect of sand drains in the foundation of the Sombar Dam in Iran on its mechanical behavior. The Sombar Dam is a project to control flooding and provide agricultural water to Gholaman city in northeastern Iran. The investigation included the mechanical behavior of the dam with vertical sand drains. The studied parameters were drain diameter, depth and spacing in addition to the vertical-to-horizontal permeability ratio (ky/kx) of the foundation soil during the time of construction of the dam using a Mohr-Coulomb (MC) model in the software application GeoStudio. The results revealed that reducing the drain spacing (increasing the number of drains) and increasing the depth and diameter of the drains led to an increase of the settlement rate (up to 90%) and the stability of the dam over a shorter period of time (24 months) compared to no drain condition. With a decrease in the ratio of vertical-to-horizontal permeability (ky/kx = 0.1) for all drain parameters there was a decrease in the value of the dam settlement rate and the safety factor
Regenerative Chatter Evaluation when Turning Nickel-based Superalloy GH4169 Using PCBN Cutting Tool
Get PDFVibration during machining operation is a major issue that lowers cutting operation efficiency. Usually high cutting forces are encountered during machining processes, consequently shortening cutting tool lifetime. Thus, the metal removable rate is reduced and a poor surface finish is produced. This issue can be overcome by selecting proper cutting parameters (cutting speed, feed, and depth of cut), especially when machining difficult-to-cut materials at high cutting speed. In this paper, a two-degrees-of-freedom turning vibration model is introduced to study the vibration mode of the system when nickel-based superalloy GH4169 is turned at varying cutting depths. The effect of varying the cutting depth on system vibration was simulated using the Matlab/Simulink software. In addition, the model was experimentally tested on a numerical controlled lathe machine. The stable limit cutting depth and the main vibration directions of the system chatter were the responses that were investigated. The results show that the simulation provided a reasonable approximation of the experimental results
Theoretical Beam Hardening Correction for Industrial X-ray Computed Tomography
Get PDFBeam hardening is a significant artifact that comes from the polychromatic nature of the X-ray source in computed tomography. It appears because the object tends to absorb more low-energy photons within the beam, which leads to a nonlinear relationship between attenuation and material thickness. As a result, the reconstructed image is spoiled. This work articulates an approach to promoting the correction of MeV X-ray beam hardening. In order to calculate the attenuation of the polychromatic beam, the following terms were evaluated: the energy spectra S(E) for sets of X-ray spectra with a maximum energy of 2, 4, 6 and 9 MeV were simulated using the Geant4 toolkit; the counting efficiency λ(E) was estimated based on the Lifton method; and the attenuation coefficient µ(E) was taken from the NIST database. The non-linear relationship between the attenuation and the thickness of iron was investigated. The beam hardening for each energy set was successfully corrected by polynomial fitting, transforming the polychromatic attenuation data into equivalent monochromatic data. The corrected attenuation was used to estimate the penetration capability of the X-ray source and produced a result that was consistent with what has been reported in the literature
An Intelligent Incentive Model Based on Environmental Ergonomics for Food SMEs
Get PDFIn this study, an intelligent incentive model based on environmental ergonomics in food small and medium-sized enterprises (SMEs) was developed. Environmental ergonomics was defined as the impact of temperature and relative humidity within a certain range on a worker's heart rate during work. Optimum environmental ergonomics are highly required as a basic standard for food SMEs to provide fair incentives. Recommendable parameters from a genetic algorithm and fuzzy inference modeling were used to model customized incentives based on optimum heart rate, workplace temperature and relative humidity before and after working. The research hypothesis stated that industries should optimize their workload and workstation environment prior to customizing incentives. The research objectives were: 1) to recommend optimum environmental ergonomics parameters for customized incentives; 2) to determine the incentives at workstations of SMEs based on optimum environmental ergonomics parameters and fuzzy inference modeling. The optimum values for heart rate, workstation temperature and relative humidity used were based on recommendable values from the genetic algorithm. An inference model was developed to generate decisions whether a worker should receive an incentive based on a calculated index. The results indicated that 84.4% of workers should receive an incentive. The results of this research could be used to promote the concept of ergonomics-based customized incentives
Determination of The Site Amplification on Deep Soil Layer Using 1-D Site Response Analysis (Case study: Jakarta City, Indonesia)
Get PDFThe dynamic response of deep soil layers is used in the development of microzonation maps. The empirical correlation between standard penetratation blow count numbers and S-wave velocity was derived for practical purposes in site characterization based on local data in a case study in Jakarta, Indonesia. For estimating the intensity of potential earthquake shaking at the ground surface as a function of depth to the bedrock surface layer, 1-D site response analysis was carried out in 5745 simulations. The site amplification values were then evaluated by dividing the spectral acceleration (SA) at ground surface by the SA at rock outcrop. Plots of the SA amplification values at interested depth intervals of the bedrock surface layer were assigned. The results showed that the site amplification values estimated by considering the local depth of the bedrock surface layer were generally smaller than the SA amplification values from the Indonesian seismic building code SNI-1726-2012. Also, there appears to exist a tendency of lower levels of mean regression of amplification, in particular for the soft soil site class
Parametric Study of One-Dimensional Seismic Site Response Analyses Based on Local Soil Condition of Jakarta
Get PDFSeismic site response analysis is used to estimate the response of soil deposits during seismic loading at any depth of interest and to interpret time histories as well as response spectra. This type of analysis involves many parameters that can affect the character of ground shaking. It is important to know the effect of these parameters in order to perform reliable seismic hazard evaluation at a site. This paper presents the effects of several parameters toward the characteristics of surface response spectra based on the local soil conditions of Jakarta using a one-dimensional (1-D) site response model with total stress approach. A parametric study was performed on two cohesive soil deposit profiles with a different site class, namely medium clay (site SD) and soft clay (site SE). The bedrock layers of both profiles were located at a depth of 300 m. In this study, the analytical methods implemented were the equivalent-linear method and the non-linear method. Several different dynamics soil models were also implemented. In addition, variation of property parameters, such as depth of bedrock, shear wave velocity of bedrock, layer thickness, etc., were studied. The results of this study indicate that all of the studied parameters have a significant effect on the response spectra at the ground surface
Seismic Response Validation of Simulated Soil Models to Vertical Array Record During A Strong Earthquake
Get PDFSeveral soil models, such as linear elastic, equivalent linear, and non-linear models, are employed in seismic ground response analysis. The aim of this study was to validate the seismic responses at ground surface of several soil models with the vertical array record of the Kobe earthquake. One-dimensional seismic response analyses were performed at Port Island using several soil models. The responses at ground surface from the simulated soil models were validated with the vertical array record of the Kobe earthquake. The results showed that the extended hyperbolic model yielded the most appropriate response according to the Kobe earthquake's recorded motion. This means that this model can be considered a suitable soil model to predict the response of strong earthquakes. In general, the results support the recommendation to select the most appropriate soil model for seismic ground response analysis
Cutter Load Distribution Analysis and Crown Shape Optimal Design of Complex Curved PDC Bit
Get PDFWhen drilling in hard rock formations, the wear of the complex curved PDC bit is extremely uneven. To solve this problem, a numerical simulation method was used to analyze the load distribution law of the cutters and the crown shape of the complex curved PDC bit was optimized. The simulation results showed that: 1) along the radial direction of the bit, the axial load on the cutters increased first and then decreased, while the radial load decreased first and then increased; 2) the axial load on the cutters was the largest at the nose and taper area of the bit, while the radial load on the cutters was the largest at the center and shoulder area of the bit; 3) the influence of the inner cone angle on the cutting load was mainly concentrated in the bit crown's inner cone area, while the influence of the outer arc radius on the cutting load was mainly concentrated in the bit crown nose and taper areas. Based on these conclusions, the crown shape of the complex curved PDC bit was optimized and a field test was carried out. The test results showed that, compared with the original complex curved PDC bit, the average bit life and drilling efficiency of the new designed bit was increased by 20% and 18%, respectively, especially in hard rock drilling. The average drilling efficiency of the new designed bit was increased by 50%
Alkaline-assisted Microwave Pretreatment of Tetraselmis suecica Biomass for Fed-batch Enzymatic Hydrolysis
Get PDFA two-part study on pretreatment and fed-batch enzymatic hydrolysis of pretreated Tetraselmis suecica using a high initial biomass concentration was conducted. First, the effect of different pretreatment processes, i.e. microwave (MC), dilute alkaline (AK), and microwave-alkaline assisted (MAK) pretreatment, on enzymatic hydrolysis of T. suecica biomass was evaluated. Furthermore, high initial biomass concentration enzymatic hydrolysis improvement via a fed-batch strategy was performed. Among the pretreatments tested, the MAK pretreatment produced the highest sugar concentration at 9.83 ± 0.24 mg/mL, corresponding to a conversion yield of up to 85.58% of carbohydrate content available in the pretreated biomass. The solid fraction generated after pretreatment was characterized using Fourier transform infrared (FTIR) spectroscopy. The FTIR analysis revealed a significant change in the functional hydroxyl and acetyl groups of the biomass, which is favorable for enzymatic hydrolysis. Introducing an initial microalgal biomass concentration beyond 15% (w/v) exhibited a low enzymatic hydrolysis yield. The fed-batch enzymatic hydrolysis strategy of the MAK pretreated T. suecica was further investigated by adding the substrate at different time intervals. The findings indicate that the fed-batch operation system could enhance sugar production and enzymatic hydrolysis yield one-fold
